The object of the invention is an electric switch or circuit breaker, in particular suitable for medium voltage, and comprising a vacuum cartridge. The term “medium voltage” (MT) is used in its usual acceptation, i.e. for a voltage that is greater than 1000 volts in alternating current and greater than 1500 volts in direct current but which does not exceed 52,000 volts in alternating current and 75,000 volts in direct current.